An attractive young man posts an ad online. Soon afterward, he is naked and face-down on the bed in a dimly lit hotel room. Throughout the night, nameless men enter through the unlocked door. Instead of saying hello, they unzip their pants. When they are finished, they leave. By sunup, the young man has lost track of how many sex partners have come and gone. If he has achieved his goal, his next test for the human immunodeficiency virus will come back positive.

On another day, a different man posts an announcement indicating the day and time that he plans to be at a local sex club, 442 Natoma. Then he kneels in a dark corner of the club — his naked silhouette barely visible — as he waits for those who want to help “convert” him.

At any given time, there are often dozens of people actively posting online ads as “chasers” or “gifters” in San Francisco and elsewhere around the nation. Some may just be fantasizing, but many are indeed willing to go through with the fantasy.

Though chasers and gifters are active around the world, many see San Francisco as a kind of mecca. With its famously liberal attitudes toward sex, thriving gay culture, and high-profile kink festivals like the Folsom Street Fair and Up Your Alley, the city is particularly attractive to members of the little-studied subculture, many of whom are spreading the virus not only among themselves but also to unsuspecting people, making the disease even more difficult — and costly — to fight.

For members of this dangerous minority, Craigslist is a popular choice to connect with one another, for obvious reasons: Posting there is free, and because almost everyone uses the site at some point or another, the ad will be seen by a relatively large number of eyeballs. Alternately, a monthly subscription to BarebackRT.com, also known as Bareback Real Time, costs $5.95. But an ad featured on that site — designed for gay men who engage in “bareback,” or condomless, sex — is likely to reach a smaller but more targeted audience. The site’s search function also makes it relatively simple for subscribers to find and communicate with those who would classify themselves “gift givers” — HIV-positive men who are seeking to “poz” others — and “bug chasers” — HIV-negative men who long to become positive. In addition, smartphone apps like Grindr and Recon, as well as the website Breeding.Zone, where gifters and chasers share advice and stories about their sexual experiences, make it relatively straightforward to meet people who want to be infected with the virus that causes AIDS — or to infect their partners.

“18 year old twink bug chaser looking to get pozzed,” reads one recent Craigslist ad posted by a Santa Clara man describing himself as single, thin, and 6-foot-3. “Total virgin here looking to experience anything and everything.”

Another ad, posted on Bareback Real Time by a 26-year-old gift-giver, reads: “After months of chasing, I tested poz. High viral load. Looking for neg bottoms [to infect].”

The text of many ads is even more explicit than these, and most are accompanied by graphic nudity.

“Impregnate me with the AIDS virus,” yet another ad reads. “This is what I live for.”

It is difficult to say exactly how many people are intentionally spreading HIV, but in any given week, in the San Francisco Bay Area personals section of Craigslist, it is not unusual to find at least a couple of personal ads by bug chasers or gift givers. On Bareback Real Time, there are often dozens of profiles that fit the description.

I don’t believe that members of the bug-chasing and gifting subculture should be criminalized or shunned. But I do believe that increased public health efforts are needed, as I suggest in the article. Ducking our heads in the sand and denying reality is not going to solve anything. We must be willing to openly discuss serious issues before we can have any hope of solving them. — Sincerely, Channing Joseph

WHAT’S MOTIVATING THE BEHAVIOR?

In researching this article, I went undercover to get a glimpse into this hidden world. I posed as a bug chaser on Bareback Real Time as well as on Grindr, the most popular gay dating app, and on Recon, another dating app specifically for men with sexual fetishes. I have not included the names of those who communicated with me out of respect for their privacy. All the chasers and gifters I found were gay or bisexual men, and they came from a variety of ethnic backgrounds and ranged in age from 18 to 59.

Over several weeks, I reached out to men whose profiles identified them as HIV-positive, zeroing in on those who said they had a “high viral load” — in other words, those whose medical tests indicated that their blood contained a large number of copies of the virus (and who would therefore be most contagious). I asked them each to have sex with me and made it clear that I was seeking to become HIV-positive.

As I had hoped, I received a handful of outright rejections, including a heartfelt one from a 28-year-old Grindr user who poignantly told me, “I nearly died of AIDS. I’m not going to purposely give someone the thing that almost killed me.”

By contrast, however, I received more than 100 messages via Bareback Real Time from men who said they were willing to have condomless sex with me — and some of whom invited me to “conversion parties” that they said they would organize at their homes or at local hotels, like the Travelodge, at the corner of Market and Valencia streets, or the Casa Loma Hotel, at Fillmore and Fell streets. Both locations are popular meeting spots for gay cruising and sex parties.

“You are too fucking hot,” one guy told me. “And I’m on a little meds break. (I have a couple of FB’s who wanted me to poz them). One is [already], the other we’re working on. Would LOVE to experience the intensity of poz fucking with you.”

“Stay negative so I know I’m the one who pozzed you,” another guy demanded. “My dick is rock hard already.”

Coming to understand how gift-giving and bug-chasing culture functions was relatively easy. Coming to an understanding of why it exists has been another matter. For what reason would anyone seek to be infected by a potentially fatal disease?

There have been very few peer-reviewed studies into what motivates men to spread HIV. In an earlier era, when infections were much more common and much deadlier, researchers like the psychologist Damien Riggs theorized that it boiled down to loneliness, that these men might be seeking out HIV infection in order to “overcome difference” and feel part of the larger gay community. But in 2016, with infections way down, that motivation seems unlikely.

Is it instead a kind of slow suicide? Is it mental illness? Is it ignorance? Perhaps not surprisingly, the answers were not clearly reducible to any pat formulas.

Rather than seeming depressed or suicidal, many of the newly positive men I spoke with indicated that they were enjoying their lives more than ever before.

Rather than being ignorant of the consequences of their actions, most seemed very informed about the risks they were taking. Of course, those risks included forgoing condoms, but some chasers also described in detail additional measures that they were taking to increase the risk of becoming infected. Some, for example, irritated their rectum with a rough toothbrush before intercourse to create abrasions.

Rather than clearly being mentally ill, some spoke relatively eloquently about why they had decided to begin “chasing.”

To be sure, HIV in 2016 is not what it was in the early 1980s. Today, being HIV-positive is no longer a guarantee of developing AIDS, and the men who seek infection do not necessarily face the horrific consequences that they once did. Nor do those to whom they pass the virus.

HIV HAS A NEW MEANING

In 1981, when the illness now known as AIDS (acquired immune deficiency syndrome) was first observed among gay men, it was called GRID, for gay-related immune deficiency. At the time, a GRID diagnosis meant near-certain death from the rare, opportunistic infections and cancers that would develop as the virus wore down the body’s natural defenses.

Thirty-five years and 35 million worldwide deaths later, things are vastly different. Better medical treatments and access to social services have helped, and San Francisco has seen HIV infections steadily drop over the last few years.

“New HIV diagnoses in San Francisco declined 17 percent from 309 in 2014 to 255 in 2015,” the city’s Department of Public Health reported in September. “Overall, 93 percent of the 17,198 people living with HIV are aware of their infection. They are being linked to care more quickly and showing improved outcomes.”

In August, the world heard even better news, as the results of new research showed that HIV treatment works better than many had previously thought. A study of roughly 1,000 couples found that HIV-positive gay men whose viral loads have been effectively suppressed by medication did not infect their HIV-negative partners, even after two years of having sex without condoms.

And at the International AIDS Conference in July, researchers announced that a promising new vaccine and “functional cures” for HIV are on the horizon.

To top it all off, the 2012 approval of Truvada — or PrEP, for pre-exposure prophylaxis — by the U.S. Food and Drug Administration has sparked seismic shifts in attitudes among many in the gay community toward sex and toward HIV-positive people. PrEP, which is meant to be a daily treatment taken by HIV-negative people who are at risk of being exposed, has been shown to prevent infections in up to 99 percent of sexual encounters with HIV-positive partners.

Essentially, it means that people who are taking PrEP should feel much less worried about contracting HIV. And in fact, that is the case for many folks, as exemplified by a public service announcement released by the city of West Hollywood in which a musical trio brightly sings “Hakuna Truvada” (wordplay based on “Hakuna Matata,” a song in Disney’s The Lion King whose title means “no worries” in Swahili).

But for some, the calculus is not so simple.

In an Oct. 28 post to a Breeding.Zone message board, one member expressed his misgivings about using Truvada, writing, “I’ve been on PrEP for something like 3 1/2 years. And I gotta say I sorta miss the risk.”

“Anyone else feel the same way?” he asked. “Part of me wants the risk — even wants to be poz. But the other part of me is making sure I take enough meds to stay neg. … Anyone else on PrEP ambivalent about PrEP?”

The question reveals a way of thinking that I observed over and over while asking numerous chasers why they were seeking to be infected.

Many of them told me that, for them, chasing is simply a form of thrill-seeking.

A 50-year-old man living in Orange County remarked, “After crossing that bridge of knowingly taking that first poz load [of semen] … I have been having the hottest sex of my life.”

When I asked him if that was the reason he said he had chosen to become HIV-positive at a conversion party in Miami over Labor Day weekend, his response was unambiguous. “Absolutely,” he said.

For others, bug chasing is a way to finally overcome a persistent fear or anxiety around sex.

“While you’re not pozzed, you keep guessing [about] it and there is still a chance you’re clean,” one man explained. “So you just wonder about it and keep yourself in some kind of fear. Once you’re poz, you’re sure about it and it all settles.”

Another less common reason cited by those I encountered was a feeling that becoming infected by a partner, or infecting a partner, was a way to establish a special, permanent bond.

A 26-year-old Marine living in Palm Springs, whom I spoke with via Recon, told me that he is taking PrEP now to prevent HIV infection but eventually plans to stop when his military obligations end, so that he can be infected by an HIV-positive partner of his choosing.

“I want to get poz’d by the guy I submit to,” he said. “When I get out is when I want to be poz’d. … I have until next October.”

When asked what the city of San Francisco is doing to address websites and apps that promote bareback sex and the spread of HIV, Rachael Kagan, a spokeswoman for the Department of Public Health, referred me to the “Our Sexual Revolution” campaign promoting PrEP, which has been featured on billboards and on ads in Muni stations and at bus stops.

She also said the city sends HIV/STD screening teams to local sex parties and creates educational profiles on some websites to do outreach directly to groups engaged in risky behaviors.

“DPH has a ‘health profile’ on Bareback Real Time that promotes the ‘Our Sexual Revolution’ PrEP campaign,” she told SF Weekly in an email. “The headline is ‘Interested in PrEP?’ and the content leads them to the campaign website: www.oursexualrevolution.org.”

Given the potential consequences, the department’s approach to outreach seems rather meek, although striking the right balance between safety and the city’s free-and-open sex culture is going to be a tough one. San Francisco has not made a practice of criminalizing HIV infection, as has occurred in some other places.

For instance, Missouri is at the other end of the spectrum. Last year, the state sentenced a former college wrestler, Michael Johnson, 23 at the time, to 30 years in prison for infecting one of his sexual partners and putting four others at risk.

Michael Petrelis, a longtime San Francisco AIDS activist and advocate for the repeal of HIV criminalization laws, has been corresponding with Johnson in prison. Petrelis tells SF Weekly that he applauds the city’s efforts to promote awareness of PrEP but says the effort falls short when it comes to making the drug affordable.

“PrEP is one vital tool of prevention but advocates … do not address the pricing of Truvada …” he says. “Yes, let’s applaud the effective prevention capability of PrEP, but we can’t overlook how much all HIV … drugs cost.” (PrEP can run to between $1,300 and $2,000 a month without insurance.)

Kagan says the city is optimistic about its efforts to reduce infection rates among residents, but she admits that more needs to be done.

“We estimate that approximately 12,500 San Franciscans are receiving PrEP,” she said. “However, we have observed important disparities in PrEP use in San Francisco, with lower uptake among youth, African Americans, and women.”

Meanwhile, on Dec. 1, people around the world will recognize World AIDS Day with concerts, conferences, and fundraisers to raise awareness and funding to combat HIV and AIDS.

A two-day National HIV PrEP Summit, the first of its kind, is set to begin on Dec. 3 at the Hilton Union Square, with researchers, advocates, and other stakeholders convening to plan future strategy to expand the reach of PrEP. On the same day, a wildly popular bareback-sex party, called CumUnion, is to be held at the sex club at 442 Natoma Street, less than a mile away.

Channing Joseph is the editor-in-chief of SF Weekly. Send him a message at cjoseph [AT] sfweekly.com, and be sure to follow him on Twitter at @cgjoseph.